1. Field of the Invention
The invention further relates to a device for carrying out this method.
2. Description of the Related Art
Methods and devices of these types are generally known in the prior art. They are used to preserve milk or breast milk intended for storage or later use and/or to remove infectious microorganisms from the milk. Methods of this type are known, for example, under the name pasteurization.
It is now generally acknowledged that feeding a baby with breast milk not only has advantages in relation to the feeding itself but also has immunological advantages, since breast milk contains, besides protein, fat and carbohydrates, inter alia the inhibins lysozyme, lactoferrin, neuraminic acid and specific immunoglobulins, especially sIgA. For this reason, breastfed children are less susceptible to infections and allergens than are nonbreastfed children.
For preterm infants in particular, feeding with breast milk thus has such great advantages that, inter alia for this reason, milk banks were set up in the 1980s for processing of breast milk and storage for later use. For this purpose, milk from various donors was pooled and then subjected to a heat inactivation or a cryoinactivation. For safety reasons, the system of milk banks has now been largely abandoned because, to prevent infections, an unambiguous coordination between the infant and its own mother's breast milk is indispensable. It is intended in this way to prevent uncontrolled transmission of infectious diseases such as HIV, hepatitis etc.
However, for feeding preterm infants, this means that their own mother's breast milk must be pumped off, processed and stored temporarily in the hospital and/or at home since, because of the immaturity and the low food intake capacity, and the frequent feeding associated therewith, these preterm infants cannot be breastfed. An additional factor is that preterm infants frequently remain three to four months in the hospital whereas the mothers are discharged only a short time after delivery, so that appropriate stocks of breast milk must be present in the hospital in order to ensure continuous feeding of the preterm infants. The technical significance of this is that even small volumes of, for example, 20 ml must be processed and stored individually.
Whereas the vertical transmission of HIV, hepatitis and other infectious diseases has become controllable through dispensing with breastfeeding, this does not apply to infections with cytomegalovirus (hereinafter: CMV) which is currently one of the commonest prenatal infections. About 10-20% of all neonates additionally acquire a perinatal infection through breast milk. The course of the illness may be very serious and, especially in preterm infants, fatal.
Vochem et al., Transmission of cytomegalovirus to preterm infants through breast milk, Pediatr Infect Dis J, 1998, Volume 17, pages 53-58, report in this connection on a clinical study in which the risk of transmission of CMV through breast milk to children with a birth weight below 1500 g or a gestational age of less than 32 weeks was investigated. About 50% of the mothers were CMV-seropositive, and 85% of these seropositive mothers excreted CMV in the breast milk, as was demonstrated by an investigation of the cell-free whey. During the study, more than half of the preterm infants breastfed by CMV-seropositive mothers became infected with CMV.
Because of the fact that the authors were able to identify infected breast milk as the only source for the transmission of CMV, they proposed that CMV in pumped-off breast milk be inactivated in order to prevent transmission and avoid an early and thus frequently symptomatic infection of preterm infants.
Besides the classical methods of holder pasteurization and cryoinactivation, the authors proposed that infected breast milk be short-term heated, for ten seconds, at 72° C. without, however, describing accurately the method they used. They report that no traces of infectious viruses were detectable after such brief heating.
In an early study, Goldblum et al., Rapid high-temperature treatment of human milk, The Journal of Pediatrics, 1984, Volume 104, pages 380-385, describe a short-time pasteurization of breast milk by which the number of bacteria and CMV was greatly reduced without destroying many of the constituents important for immunology and nutrition. In the known method, milk from a plurality of donors is pooled (1,2 to 21) and heated by a plate heat exchanger. Since the heat exchanger was designed for treating large volumes of cow's milk, the pooled human milk was injected into a continuous stream of sterile distilled water and heated at 72° C. for 5 seconds, with the desired temperature being reached within less than three seconds. The samples were then cooled to 2° C. within three seconds.
The use of an apparatus which is customary in the dairy industry and has the required large sample volume means that the known method does not comply with the current requirements mentioned at the outset for the treatment of small sample volumes.
In another early study, Dworsky et al., Persistence of cytomegalovirus in human milk after storage, The Journal of Pediatrics, 1982, Volume 101, pages 440-443, report that a holder pasteurization, that is to say heating the milk at 62° C. for 30 minutes leads to complete elimination of CMV from CMV-seropositive milk. However, they mention that this treatment is not ideal if the immunological properties of the milk are to be retained. The pasteurization at a lower temperature, namely 56° C., which was therefore investigated did not, however, show satisfactory elimination of CMV from infected milk.
The results obtained by the authors with cryoinactivation, in which the samples were stored at −20° C. overnight, were likewise unsatisfactory.